1. Field of the Invention
The invention relates in general to an electronic device, and more particularly to an electronic device, which fastens a navi-key with a function-key tightly.
2. Description of the Related Art
With the rapid advance in science and technology, electronic devices are widely used nowadays. With the advantageous features of slimness, compactness, handiness and portability, portable electronic devices have become an indispensable appliance to modern people in their everyday lives. Portable electronic devices, such as personal digital assistant (PDA) and mobile phone, have a wide range of varieties. With an electronic device at hand, a user can make or answer a phone call, make or edit a memo, look up a dictionary or listen to the music whenever and wherever the user feels like to. The availability of electronic devices really brings about a great convenience to modern people in their everyday lives and shortens the distance between people in terms of communication.
Referring to FIG. 1A and FIG. 1B at the same time. FIG. 1A is a front view of a conventional mobile phone, while FIG. 1B is a rear view of the navi-key and the function-key in FIG. 1A. In FIG. 1A and FIG. 1B, mobile phone 10 includes a housing 11, a display panel 12 and a keypad 30, of which, the keypad 30 further includes a navi-key 13, function-keys 14˜18 and a number of operation keys 19. The housing 11 has a housing's front surface 11a on which the display panel 12, the navi-key 13, function-keys 14˜18 and operation keys 19 are disposed, wherein the navi-key 13 and function-keys 14˜18 are inter-connected and disposed between the display panel 12 and operation keys 19. The navi-key 13 further includes a front portion 13a and a back portion 13b, wherein the back portion 13b is disposed on the backside of the front portion 13a while the edge of the back portion 13b almost shares the same cut surface with the edge of the front portion 13a. These function-keys 14˜18 correspondingly include front portions 14a˜18a and back portions 14b˜18b, wherein these back portions 14b˜18b are correspondingly disposed on the backside of these front portions 14a˜18a while the edges of back portions 14b˜18b almost respectively share the same cut surface with the edges of front portions 14a˜18a. 
As shown in FIG. 1B, the edge of the back portion 13b has a squared protruding portion 13c protruding out of the edge of the front portion 13a and indentations 13e˜13h, wherein these indentations 13e˜13h expose a part of the backside of the front portion 13a while indentations 13e and 13f are formed at both sides of the squared protruding portion 13c. With regard to function-keys 14˜18, the edges of back portions 14b˜18b respectively have protruding portions 14c˜18c respectively protruding out of the edges of front portions 14a˜18a. The back portion 16b of the function-key 16 has an indentation 16d and two protruding portions 16e and 16f protruding out of the edge of the front portion 16a, wherein the indentation 16d is formed between the protruding portion 16e and 16f for exposing a part of the backside of the front portion 16a. 
As shown in FIG. 1C, when navi-key 13 is connected with function-keys 14˜18, protruding portions 14c and 18c are respectively inserted into indentations 13g and 13h, protruding portions 15c and 16e are inserted into the indentation 13e, protruding portions 16f and 17c are inserted into the indentation 13f, the squared protruding portion 13c is inserted into the indentation 16d. It is noteworthy that the squared protruding portion 13c is merely inserted into the indentation 16d without any buckling design. That is to say, when dragged by a pulling force along the direction of the arrow 50 in FIG. 1B and the direction of the arrow 60 in FIG. 1C, the squared protruding portion 13c will be detached from the indentation 16d. 
When the mobile phone 10 in FIG. 1A drops off to the ground or is hit by an external force, the back portion 13b will be extended and deformed by a colliding force. Since the squared protruding portion 13c is merely inserted into the indentation 16d, the squared protruding portion 13c will be detached from the indentation 16d when the back portion 13b is extended and deformed. Under this circumstance, the navi-key 13 will hump up or even become disconnected from the housing's front surface 11a in FIG. 1A, severely affecting the exterior of the mobile phone 10 and the operating function of the keypad 30.